—Measurement of force-frequency relationship (FFR) is useful in the evaluation of heart rate–dependent contractile dysfunction. The purpose of this study was to evaluate a new Doppler-derived method for assessing FFR. Doppler velocity spectra at the left ventricular (LV) outflow tract was used to estimate mean blood flow velocity (mBFV), ejection time (ET) and velocity-time integral. LV ejection force (LVF) was then calculated according to the law of conservation of momentum: 1060 kg/m3 3 (mBFV[m/sec]/ET [s]) 3 Stroke volume (mL). A symptom-limited, graded, bicycle semi-supine exercise test was performed in 56 patients with LV dysfunction (LVejection fraction527 ± 6%). Measurements were obtained at baseline and serially during the test. The change in FFR was defined as up-sloping when the peak LVF was higher than the baseline value. The change was biphasic when the trend was initially up-sloping, then down-sloping; it was flat or negative when peak LVF was less than the baseline value. LVF was 30 ± 12 mN in patients with up-sloping FFR (n 5 39) and 15 ± 6 mN in those with biphasic or flat FFR (n 5 17; p , 0.0001). The ultrasound assessment of the FFR was highly concordant with a previously validated method based on pressure-end-systolic volume index ratio (k 5 0.75; 95% confidence interval, (0.55–94.0). The evaluation of the LVF using Doppler is an alternative method for the assessment of FFR during stress echocardiography in patients with LV dysfunction.

Ultrasound Assessment of the Force-frequency Relationship from the Law of Conservation of Momentum in Patients with Left Ventricular Dysfunction.

PEDRIZZETTI, Gianni;
2013

Abstract

—Measurement of force-frequency relationship (FFR) is useful in the evaluation of heart rate–dependent contractile dysfunction. The purpose of this study was to evaluate a new Doppler-derived method for assessing FFR. Doppler velocity spectra at the left ventricular (LV) outflow tract was used to estimate mean blood flow velocity (mBFV), ejection time (ET) and velocity-time integral. LV ejection force (LVF) was then calculated according to the law of conservation of momentum: 1060 kg/m3 3 (mBFV[m/sec]/ET [s]) 3 Stroke volume (mL). A symptom-limited, graded, bicycle semi-supine exercise test was performed in 56 patients with LV dysfunction (LVejection fraction527 ± 6%). Measurements were obtained at baseline and serially during the test. The change in FFR was defined as up-sloping when the peak LVF was higher than the baseline value. The change was biphasic when the trend was initially up-sloping, then down-sloping; it was flat or negative when peak LVF was less than the baseline value. LVF was 30 ± 12 mN in patients with up-sloping FFR (n 5 39) and 15 ± 6 mN in those with biphasic or flat FFR (n 5 17; p , 0.0001). The ultrasound assessment of the FFR was highly concordant with a previously validated method based on pressure-end-systolic volume index ratio (k 5 0.75; 95% confidence interval, (0.55–94.0). The evaluation of the LVF using Doppler is an alternative method for the assessment of FFR during stress echocardiography in patients with LV dysfunction.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2681749
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